<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        span {
            color: blue;
        }
    </style>
    <link href="css/demo.css" rel="stylesheet">
</head>
<body>
<div style="color: red">hello css</div>
<span>hello css</span>
<p>hello css</p>
</body>
</html>